1. Field of the Invention
This Invention relates to rocker arm assemblies for a valve train of an internal combustion engine, and more particularly, to a bearing arrangement used in a pedestal mounted rocker arm assembly used in a push rod style engine.
2. Related Art
Pedestal mounted rocker aim assemblies have a rocker arm rotatably mounted on a support pin and the support pin is fixed to the cylinder head through the pedestal. The support pin is also known as a trunnion. Typically, the support pin rests on a support block which positions the overall rocker am assembly away from the cylinder head. One end of the rocker arm is in contact with the push rod while the other end of the rocker arm is in contact with the valve shaft.
A radial bearing arrangement is formed between the support pin and the rocker am to facilitate rotational movement of the rocker arm on the support pin. The radial bearing arrangement handles the radial forces from the rocking motion of the rocker arm on the support pin.
Rocker arm assemblies can also be subject to axial forces. These axial forces can occur when certain parts are out of alignment, for example the rocker arm pallet and the socket, the lower end of the pushrod and the socket, or the value shaft and the rocker arm pallet.
One solution to handle axial forces in rocker arm assemblies is disclosed in U.S. Pat. No. 6,694,936, issued Feb. 24, 2004. The '936 patent uses an axial roller bearing arrangement to handle axial forces. In one embodiment taught in the '936 patent the axial roller bearing is positioned between the radial roller baring and the fastening bolt, and a thrust washer is positioned between the axial roller bearing and the fastening bolt.
There is a need to provide alternative arrangements for rocker arm assemblies that can handle both radial forces and axial forces.